It is known to control machines, for example land, sea or air vehicles, using stick controllers. In particular, aircraft are fitted with passive stick controllers (i.e. inceptors or “joy sticks”).
For aircraft, there are currently two types of side stick controllers in use that provide pilot inputs into a vehicle's control system (e.g. its Flight Control System). One type is “passive” and the other is “active”.
Passive inceptors have fixed force/feel characteristic that are provided by springs and dampers, but do not provide tactile cues about the aircraft's current situation to the pilots. Flight control systems that use passive side sticks rely on the flight control laws within the aircraft's Flight Control System to keep the aircraft within a safe operating envelope. That is, the Flight Control System does not allow the aircrafts' limits to be exceeded, whatever inputs the pilot applies to the system via the sticks control. This is sometimes referred to as “carefree” handling.
Active inceptors are more complex. In addition to springs and dampers that are used to provide a reversionary force/feel characteristic, they also have a servo-actuator mechanism that allows the force/feel characteristic of the stick to be continuously modified throughout a flight.
Movement of either passive or active inceptors generates positional information which is interpreted to control the vehicle. If the inceptor mechanism jams (for example, due to mechanical failure) then the operator is not able to move the inceptor, and hence no positional data will be generated and the vehicle cannot be controlled.
For land or water based vehicles, while serious, this problem may be mitigated by shutting down the vehicle so as to come to a halt. For many aircraft, the problem may be mitigated by provision of a second set of controls, which is commonplace as many air vehicles have two flight control positions, and the chance of both failing at the same time is very small.
However, for aircraft having only one set of controls, or dispatched with only one pilot, there is a customer need to further mitigate the problem of inceptor jamming.
Hence an inceptor apparatus with a failsafe which provides for control of a vehicle (for example an aircraft) in the event of the inceptor becoming physically immovable, and hence unable to produce positional inputs to a control system for the aircraft, is highly desirable.